Copper is an essential metal nutrient that plays important roles in human health, aging, and disease. The potent redox activity of copper is required for a diverse array of physiological processes ranging from respiration to antioxidant defense to wound healing. At the same time, however, unregulated imbalances in copper homeostasis can contribute to metabolic diseases like obesity and diabetes as well as cancer, heart disease, and neurodegenerative disorders, often through aberrant oxidative stress and damage pathways. We are developing and applying new chemical tools for molecular imaging of copper in living systems with the long-term goal of understanding how and in what context this metal contributes to normal physiology as well as aging and disease. This competitive renewal application will focus on elucidating the roles of copper in lipolysis, a central process i lipid metabolism that is essential for maintaining the body's energy stores but also contributes to metabolic diseases such as obesity and diabetes. Specific aims include: developing new fluorescent copper sensors with enhanced photostability to monitor of copper dynamics and a broader range of binding affinities to access a broader range of copper pools in cells, applying these new chemical tools to probe the contributions of copper signaling to lipolysis in adipocyte cell models, and biochemical characterization of newly identified copper-protein targets that mediate lipolytic signaling pathways.